The ultimate goal of this research proposal is to develop a methodology for the measurement of low picomolar (pM) concentrations of substance P (SP) and its metabolites in highly ionic biological fluids. The first goal of this proposal is to develop a preconcentration and desalting method to permit the detection of low-to-subpicomolar levels of SP and its metabolites. This will be accomplished by evaluating several different types of solid phase resins and membranes for their effectiveness in retaining low concentrations of SP from biological matrixes. The second goal of this research is to use this preconcentration/desalting methodology in conjugation with capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection operating with either pre or postcolumn derivatization. Once these goals have been met, it will be possible to investigate the transport and metabolism of SP across the Blood Brain Barrier using microdialysis sampling of the brain. Later work will compare the detection limits achievable by the developed CE/LIF methodology to those obtainable by capillary liquid chromatography (CLC) with mass spectrometric (MS) detection. Future studies will work toward the construction of an inclusive microfabricated system that contains the preconcentration/desalting device, separation capillary, and detection system.